fixed possible npe
1) Renamed values-zh values-zh_rCN in accordance with #329 and Android conventions
2) Added arrays.xml translations for Simplified Chinese (zh_rCN)
3) Added translations (arrays.xml and strings.xml) for Traditional Chinese (zh_rTW)
Merge pull request #518 from isaackwan/translation_zhrCN-TW2

Chinese Translation fixes
revised tablet ui. fixed #423
bug fixes
fixed chinese translations
let's own otr-fingerprint copy to clipboard.
minor graphic tweaks in copy otr fingerprint to clipboard
implemented ping (xep-0199) fixed #517
minor ui tweak
reset pending subscription request
added missing status messages after message scroll
no dns retry after nosrv error
fixed an 'activity has leaked window'
sending initial ping before going online after login/resume to ensure that all presences and messages have been loaded
end otr session instead of only resetting
fixed #510
MUC: differentiated a few more errors.
Merge pull request #523 from betheg/leaked_window

fixed an 'activity has leaked window'
Merge pull request #524 from betheg/muc_errors_conditions

MUC: differentiated a few more errors.