close mDb when dbhelper is closed to prevent 'Database wasn't closed properly' errors in later database openings
update targetSdkversion to 19
add initial Settings page skeleton, move the changeLockTimeout setting there
implement showLines setting
implement fully Settings Activity and add cacheword vibrate setting as well
move some variables to NConstants
fix home button in settings not working on old android versions
update to SQLCipher-for-Android v3.0.2

https://s3.amazonaws.com/sqlcipher/SQLCipher+for+Android+v3.0.2.zip
sha256: 9557d3acfe5f5e251c9bcf498e7ecd792dba6938ed8b059c80faf06fc142aa7b
sha1: ff13f24561b334a9e9ff7cf4e448943b16c7e8fe
md5: e70dcc385bae732ae93045887cd270ec

fixes #2884 fixes #24