AndroidViewClient/culebra version 4.6.0: now 100% pure python

AndroidViewClient/culebra v4.6.0 has been released bringing major improvements closing the gap with the existing APIs. This is demonstrated by the example scripts migrated to use AdbClient now, instead of MonkeyDevice.
monkeyrunner seems much farther in the rearview mirror.

changelog

• AdbClient: Added isLocked() method to check if screen is locked
• Fixed #55: drag doesn't work for old Android versions
• Removed sys.path manipulation not needed for python
• Read ANDROID_ADB_SERVER_PORT environment variable to set adb PORT. This variable is set by Jenkins Android Emulator plugin.
• Merge pull request #56 from knorrium/clean-whitespaces
• Check for sys.executable that may be not available on Windows
• Examples modified to use python
• Marked jar file creation as deprecated
• Improved UTF-8 treatment in messages
• AdbClient.startActivity() raises exception on errors
• Warns if modules are imported using 'monkeyrunner'
• Added image comparison
• Decode used only on python's 8-bit strings
• Restored obtainAdbPath() used for android API <= 16
• Trap exception generated by integer division by zero in takeSnapshot()
• Fixed famebuffer exception