tools v6.2.0

Lots of minor changes.

• Added automatic retrieval of B&N key from nook Study log file
• Added in latest version of obok plugin for Kobo kePubs
• Fix for ePubs with non-ASCII internal files names (thanks to Jose Luis)
• Fixed preferences creation for Mac DeDRM app on Mac OS X 10.10
• Fix problem initialising DeDRM plugin
• Fix problem when trying several B&N keys in DeDRM plugin
• More logging of errors in DeDRM plugin
• Better handling of PDF decrypting in DeDRM plugin
• Updated ReadMes