Bug 11238: contruct links to the appropriate manual version dynamically

Bug 11238: contruct links to the appropriate manual version dynamically

This patch uses the version number of the Koha database to
dynamically generate links from help to the appropriate version
of the manual.

Test plan (for 3.15 branch):
- Open a help page
- Verify the manual link is correct (point to 3.14 manual)
- change the version in mysql:
update systempreferences set value="3.1600000" where variable="version";
- Verify the manual link now points to the future 3.16 manual.

Signed-off-by: Bernardo Gonzalez Kriegel <bgkriegel@gmail.com>
Work as described. No koha-qa errors

Tested on top of Bug 10671
On master (BD version 3.13.xxx) help links point to 3.12 manual
Changing version to 3.14/15 points to 3.14 manual
Changing version to 3.16 points to the future :)

Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
(cherry picked from commit 572c586793548988279ce908e951146d356f0322)
Signed-off-by: Fridolin SOMERS <fridolin.somers@biblibre.com>