tmf: Update histogram text controls

tmf: Update histogram text controls

- 'Current Event' text control replaces with 'Selection Start' and
'Selection End' controls
- Text control layout updated
- Added link button to force single selection time
- Added selection span to histogram tool tip when mouse hovers over
selection range
- Fixed text control to support keypad Enter key
- Fixed to ignore invalid window span value
- Externalized tool tip messages

Change-Id: I2158dd579b2e508b3c2d0332aedc6b34626e6feb
Signed-off-by: Patrick Tasse <patrick.tasse@gmail.com>
Reviewed-on: https://git.eclipse.org/r/18634
Tested-by: Matthew Khouzam <matthew.khouzam@ericsson.com>
Reviewed-by: Matthew Khouzam <matthew.khouzam@ericsson.com>
IP-Clean: Matthew Khouzam <matthew.khouzam@ericsson.com>
Tested-by: Hudson CI
Tested-by: Alexandre Montplaisir <alexmonthy@voxpopuli.im>
Tested-by: Marc-Andre Laperle <marc-andre.laperle@ericsson.com>