Updated build script to run Lint

The build will fail if Lint exits with an error, that should ensure for example
that APIs incompatible with the target are not used.
[issue #174] Japanese translation thanks to hayashi.yuu
[issue #154] Ensure exported tracks comply to GPX schema

Aside: Added tests project to start writing unit tests.

Added GPX export test that compares output with an expected file. I also tried
to validate the XML file against the GPX schema, but that looks to be a pain
on Android as there's no built-in validator implementation.
Added Eclipse project files for test project
Updated build.xml to latest SDK version
[issue #177] Minor FR fixes thanks to christophegragnic
[issue #180] View waypoints list in track details, thanks to jdmonin
[issue #185] Sort track list by descending date by default
[issue #158] Possible fix for service being killed by ActivityManager

Applied workaround from http://code.google.com/p/android/issues/detail?id=14340
I had to bump the SDK version to 7 (Android 2.1) unfortunately.

Hard to test unfortunately, but it can't hurt.
[issues #158 #161 #182] Possible fix for background service stopping

Use Service.startForeground() as it's intended for services that are not
supposed to be killed like media players, or GPS trackers. Seems to fix
the issue in my manual tests with the emulator.
Fixed Lint warnings + added accessibility descriptions
Added project URL in GPX header
Preparing release v0.5.8
[issue #168] Fix for GPX files not visible on external storage

Force the media scanner to scan the newly created GPX file.
[issue #179] Mass export of tracks
[issue #43] Initial work on OSM upload: Additional track fields
[issue #43] Further work on OSM upload

Implemented OAuth and upload. Basics are working but still needs a lot of
work (error handling, better UI, ...).
[issue #43] Store OAuth token/secret in preferences

Will prevent OSMTracker to ask the user to log in OSM and authorize OSMTracker
for each upload.
Update res/values-pl/strings-preferences.xml

corrected mindless string translations :)
Update res/values-pl/strings.xml