add Liberapay: field with username as data

Liberapay was originally included using a numeric ID, since they had
not yet finalized the public URLs.  Now it is a username.  So this
logic prefers the username in Liberapay: field, and keeps the old
LiberapayID: to ease migration.  LiberapayID: will not override
Liberapay:.  Clients are expected to prefer Liberapay: over LiberapayID:

# Conflicts:
#	fdroidserver/update.py
#	tests/metadata/info.guardianproject.checkey.yml
#	tests/metadata/obb.main.oldversion.yml
#	tests/metadata/org.adaway.yml
#	tests/update.TestCase

tests/metadata/dump/com.politedroid.yaml

@@ -17,6 +17,7 @@ Disabled: null
 Donate: null
 FlattrID: null
 IssueTracker: https://github.com/miguelvps/PoliteDroid/issues
+Liberapay: null
 LiberapayID: null
 License: GPL-3.0-only
 Litecoin: null

tests/metadata/dump/org.adaway.yaml

@@ -40,7 +40,8 @@ Disabled: null
 Donate: http://sufficientlysecure.org/index.php/adaway
 FlattrID: '369138'
 IssueTracker: https://github.com/dschuermann/ad-away/issues
-LiberapayID: null
+Liberapay: null
+LiberapayID: '1234567890'
 License: GPL-3.0-only
 Litecoin: null
 MaintainerNotes: ''

tests/metadata/dump/org.smssecure.smssecure.yaml

@@ -37,6 +37,7 @@ Disabled: null
 Donate: null
 FlattrID: null
 IssueTracker: https://github.com/SMSSecure/SMSSecure/issues
+Liberapay: null
 LiberapayID: null
 License: GPL-3.0-only
 Litecoin: null

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

@@ -24,6 +24,7 @@ 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

tests/metadata/info.guardianproject.checkey.txt

@@ -5,6 +5,7 @@ Source Code:https://github.com/guardianproject/checkey
 Issue Tracker:https://dev.guardianproject.info/projects/checkey/issues
 Translation:https://www.transifex.com/otf/checkey
 Bitcoin:1Fi5xUHiAPRKxHvyUGVFGt9extBe8Srdbk
+Liberapay:GuardianProject
 
 Auto Name:Checkey
 

tests/metadata/obb.main.oldversion.txt

@@ -2,6 +2,7 @@ Categories:Development
 License:GPL-3.0-only
 Source Code:https://github.com/eighthave/urzip
 Bitcoin:1Fi5xUHiAPRKxHvyUGVFGt9extBe8Srdbk
+Liberapay:12334
 
 Auto Name:OBB Main Old Version
 

tests/metadata/org.adaway.json

@@ -22,6 +22,7 @@
     "Donate": "http://sufficientlysecure.org/index.php/adaway",
     "FlattrID": "369138",
     "IssueTracker": "https://github.com/dschuermann/ad-away/issues",
+    "LiberapayID": "1234567890",
     "License": "GPL-3.0-only",
     "Provides": "org.sufficientlysecure.adaway",
     "Repo": "https://github.com/dschuermann/ad-away.git",

tests/repo/index-v1.json

@@ -104,6 +104,7 @@
         "Development"
       ],
       "suggestedVersionCode": "99999999",
+      "liberapay": "12334",
       "license": "GPL-3.0-only",
       "name": "OBB Main Old Version",
       "sourceCode": "https://github.com/eighthave/urzip",