Fixes NEMO#642

Fixes NEMO#642: Double tap on a tab makes it disappeared
Merge pull request #1 from b7k/master

Fixes NEMO#642
[voicecall] Fixed segfault in voicecall manager.

Signed-off-by: Tom Swindell <t.swindell@rubyx.co.uk>
[voicecall] Updated hold interface API for more robust usage.

Signed-off-by: Tom Swindell <t.swindell@rubyx.co.uk>
[voicecall] Implemented telepathy hold interface handling

Signed-off-by: Tom Swindell <t.swindell@rubyx.co.uk>
[voicecall-ui] Use a PageHeader instead of custom images
[voicecall-ui] Use a ViewPlaceholder to indicate an empty call log
[voicecall-ui] Correct capitalisation & make consistent
[voicecall-ui] Use theme version of icon-m-common-backspace
[voicecall-ui] Remove unused image asset
[voicecall-ui] Remove icon that doesn't work.
Merge pull request #2 from rburchell/master

UI updates
Merge pull request #3 from rburchell/master

UI updates