lami.chart: use formatter on x axis for continuous data type

lami.chart: use formatter on x axis for continuous data type

Swt bar chart use categories instead of tick simply format categories
label while constructing the map.

Change-Id: I80bbf0b06a65e716a4ae87b06bc0731bb827c6dc
Signed-off-by: Jonathan Rajotte <jonathan.rajotte-julien@efficios.com>
Reviewed-on: https://git.eclipse.org/r/79577
Reviewed-by: Hudson CI
Reviewed-by: Matthew Khouzam <matthew.khouzam@ericsson.com>
Reviewed-by: Alexandre Montplaisir <alexmonthy@efficios.com>
Tested-by: Alexandre Montplaisir <alexmonthy@efficios.com>