Migrated to Android Studio/gradle

* moved all dependencies to gradle instead of shipping .jar files in the app/lib directory
* switched to official Android port of HttpClient instead of httpclientandroidlib
* new .gitignore and project files
Merge remote-tracking branch 'origin/master' into android-studio

Conflicts:
	.gitignore
Merge with origin/master
Remove Debug settings activity

* remove debug settings activity; logging can now be enabled via adb setprop, since that's the default way of enabling verbose logs in HttpClient's Android flavour and adb is required for viewing the logs anway
* update i18n accordingly
Re-enable tests again
shrink bytecode with ProGuard for both debug/release builds (closes #202)

* enable ProGuard for debug builds because real-life testing is done with debug builds
version bump to 0.6.9

* fix i18n
Use HttpClient HC4 classes whenever possible (instead of stock Android HttpClient 4.0-beta classes); reorganize imports
Temporarily use patched version of HttpClient-Android 4.3.5 to avoid Basic Authorization bug
Minor code tweaks (by lint)