Remove slider for increments as the increments should better be
left to "auto" and rarely modified (setting a value means it will
use a limitied amount of increments, but auto effectively means
as much as it is needed and can use the native backend for
drawing).

OTOH use a slider for setting the "angle" as it is already present
in hatch tab page. Angle needs a slider as it is usually one of
the main properties of a gradient (especially linear).

Increase the tab pages a bit (10px on every side) to have a bit of
breating space for all the widgets.

Change-Id: I66167fe2c97b53bc3627237279332bdd59fb03d7
Reviewed-on: https://gerrit.libreoffice.org/70175
Tested-by: Jenkins
Reviewed-by: Tomaž Vajngerl <quikee@gmail.com>