eliminate app.builds everywhere, it should be app['Builds']

The .txt format was the last place where the lowercase "builds" was used,
this converts references everywhere to be "Builds".  This makes it possible
to load metadata YAML files with any YAML parser, then have it possible to
use fdroidserver methods on that data, like metadata.write_metadata().

The test files in tests/metadata/dump/*.yaml were manually edited by cutting
the builds: block and putting it the sort order for Builds: so the contents
should be unchanged.

```
sed -i \
 -e 's/app\.builds/app.get('Builds', \[\])/g' \
 -e "s/app\.get(Builds, \[\]) =/app\['Builds'] =/g" \
 -e "s/app\.get(Builds, \[\]) =/app\['Builds'] =/g" \
 -e "s/app\.get(Builds, \[\])/app.get('Builds', \[\])/g" \
 -e "s/app\.get('Builds', \[\])\.append/app\['Builds'\].append/g" \
 -e "s/app\['builds'\]/app.get('Builds', [])/g" \
 */*.*
```

tests/metadata/dump/org.videolan.vlc.yaml

@@ -7,61 +7,7 @@ AutoName: VLC
 AutoUpdateMode: None
 Binaries: null
 Bitcoin: null
-Categories:
-- Multimedia
-Changelog: ''
-CurrentVersion: 1.2.6
-CurrentVersionCode: '1030005'
-Description: 'Video and audio player that supports a wide range of formats,
-
-  for both local and remote playback.
-
-
-  [http://git.videolan.org/?p=vlc-ports/android.git;a=blob_plain;f=NEWS NEWS]
-
-  '
-Disabled: null
-Donate: http://www.videolan.org/contribute.html#money
-FlattrID: null
-IssueTracker: http://www.videolan.org/support/index.html#bugs
-Liberapay: null
-LiberapayID: null
-License: GPL-3.0-only
-Litecoin: null
-MaintainerNotes: 'Instructions and dependencies here: http://wiki.videolan.org/AndroidCompile
-
-  see http://buildbot.videolan.org/builders/ for version code scheme
-
-  The VLC srclib commit can be found out from TESTED_HASH value in compile.sh
-
-
-  On new releases remove the updatecheck and force the CV to the last working
-
-  build. This will make sure users don''t get notified about the update until
-
-  the final build from the BS has been reviewed and tested. Once done, undo
-
-  those changes.
-
-  '
-Name: null
-NoSourceSince: ''
-OpenCollective: null
-Provides: null
-Repo: git://git.videolan.org/vlc-ports/android.git
-RepoType: git
-RequiresRoot: false
-SourceCode: http://git.videolan.org/?p=vlc-ports/android.git;a=summary
-Summary: Media player
-Translation: ''
-UpdateCheckData: null
-UpdateCheckIgnore: null
-UpdateCheckMode: Tags
-UpdateCheckName: null
-VercodeOperation: '%c + 5'
-WebSite: http://www.videolan.org/vlc/download-android.html
-added: null
-builds:
+Builds:
 - androidupdate:
   - .
   - ../java-libs/SlidingMenu
@@ -2444,6 +2390,60 @@ builds:
   timeout: null
   versionCode: '1030005'
   versionName: 1.2.6
+Categories:
+- Multimedia
+Changelog: ''
+CurrentVersion: 1.2.6
+CurrentVersionCode: '1030005'
+Description: 'Video and audio player that supports a wide range of formats,
+
+  for both local and remote playback.
+
+
+  [http://git.videolan.org/?p=vlc-ports/android.git;a=blob_plain;f=NEWS NEWS]
+
+  '
+Disabled: null
+Donate: http://www.videolan.org/contribute.html#money
+FlattrID: null
+IssueTracker: http://www.videolan.org/support/index.html#bugs
+Liberapay: null
+LiberapayID: null
+License: GPL-3.0-only
+Litecoin: null
+MaintainerNotes: 'Instructions and dependencies here: http://wiki.videolan.org/AndroidCompile
+
+  see http://buildbot.videolan.org/builders/ for version code scheme
+
+  The VLC srclib commit can be found out from TESTED_HASH value in compile.sh
+
+
+  On new releases remove the updatecheck and force the CV to the last working
+
+  build. This will make sure users don''t get notified about the update until
+
+  the final build from the BS has been reviewed and tested. Once done, undo
+
+  those changes.
+
+  '
+Name: null
+NoSourceSince: ''
+OpenCollective: null
+Provides: null
+Repo: git://git.videolan.org/vlc-ports/android.git
+RepoType: git
+RequiresRoot: false
+SourceCode: http://git.videolan.org/?p=vlc-ports/android.git;a=summary
+Summary: Media player
+Translation: ''
+UpdateCheckData: null
+UpdateCheckIgnore: null
+UpdateCheckMode: Tags
+UpdateCheckName: null
+VercodeOperation: '%c + 5'
+WebSite: http://www.videolan.org/vlc/download-android.html
+added: null
 comments: {}
 id: org.videolan.vlc
 lastUpdated: null