Add `enableDectionAppKillWhileInForeground` option to BITCrashManager

This option implements basic heuristics to detect if the app got killed by the iOS watchdog while running in foreground, which can only happen if:
- The app tried to allocate too much memory
- Main thread doesn't respond for some time

It is not possible to detect all cases where such kills can occur.
Multiple improvements for heuristic based kill detection handling

- Marked the feature as `EXPERIMENTAL`
- renamed property to `enableAppNotTerminatingCleanlyDetection`
- Added details about the heuristic algorithm
- Added optional delegate to let the developer influence if a report should be considered as a crash or not
- Adjusted the description string in the generated report to make it more clear what actually happened.
Make sure the flag that a memory warning was received is persisted right away

NSUserDefaults may not synchronize changes immediately, so if the kill happens before it persists changes, the information is lost.
Add a new line at the end of the `application specific information` string to be considered by the servers grouping
Added Photo Picker functionality to Feedback Composer (#3)
Merge branch 'refs/heads/develop' into feature/LowMemoryKills
+ Finalized preliminary feedback support. Now comes the polish.
+ Fixes a warning
Merge branch 'refs/heads/develop' into feature/LowMemoryKills
+ Changing machines..
+ Fixes File upload.
+ File persistence for Attachments
+ Original Filename of picked image is used as attachment name.
Added Delete/Edit ActionSheet
Fixed a Bug where the Feedback cannot be sent if no text is entered.
+ Improved Persistence handling.
Merge branch 'release/3.5.4' into develop
Merge branch 'refs/heads/develop' into feature/enableAppNotTerminatingCleanlyDetection
Fix referencing wrong property name
If BITAuthenticator is set to BITAuthenticatorIdentificationTypeWebAuth then also attach the user email to crash reports
Remove #ifdef for clang analyzer since the false warning from 4.2b3 doesn't appear any longer

Tested with Xcode 5.0.2