Touching startup failure notification now shows details

The text of the startup failure notification is unhelpful due to lack of
space. Touching the notification now launches an activity that gives details
of the problem and what can be done about it.

Closes #38

See merge request !7

Build with SDK 23, continue to target SDK 22. #162

This will allow people to download Android Studio, check out and build the project without extra steps. Compiling with the latest SDK is recommended even if your target is older (as ours is).

See merge request !6

H2 was failing to load its driver class on OpenJDK 6 because the code was compiled for Java 7.

The text of the startup failure notification is unhelpful due to lack of
space. Touching the notification now launches an activity that gives details
of the problem and what can be done about it.

Closes #38

Show setup page error messages by the relevant text box

Closes #159 

See merge request !3

Hide password strength meter when confirming password

Closes #100

I opted to hide the strength meter because:

* more extensive changes would have been required to set the strength meter to 100% red.
* IMHO it would lead to confusion as to the meaning of the strength meter.
* the "passwords do not match" error should eventually become a proper error of the confirm EditText, not a separate label.

See merge request !2

Clear the password field if wrong password is entered

Closes #150

See merge request !1

"synchLock" will become confusing when we have lots of objects with "sync" in the name.

This breaks backward compatibility for the wire protocol and messages
stored in the database. The database schema version has been
incremented.