Added Tecla shield keyboard-based switch event detection.
Uncommented SwitchEvent receiver.
Made switch event provider available in TeclaAccesssibilityService.
Modified single-switch touch interface to use switch event provider.
Handled mapped actions for switch events.
Connected Tecla shield Switch E1 events to switch event provider.
Added switch E2	events to the switch event provider.
Modified SHIELDEVENT_TIMEOUT to send key only if one key is detected.
Added a TODO comment at the location of joystick switch detection.
Merge branch 'develop' of https://github.com/idrc/tecla-framework into issue-182

Conflicts:
	package/tecla/keyboard/TeclaAccessibilityService.java
Merge pull request #183 from ericwan78/issue-182

fixes #182