Enable printing of profile tables

[Lubomir I. Ivanov]

here are 4 patches that enable the printing of tables under
profiles. they also include some other small additions and fixes.

the print dialog controls that are used to set the
position and dimensions of this printing mode
(GTK ver and the current/TEMP. dialog) are not active
and i'm not sure we want them enabled for the next major release?

basically, ATM the table has a fixed height with small font sizes
and row heights arbitrarily based on the font; it's does however
fit a provided width.

the sum of all rows is the fixed table height which is subtracted
from the reserved height for a dive on a page and this results
in the profile height + some padding. so instead of controlling profile
and profile-table dimensions and offsets, perhaps we can
enable font sizes (which will adjust table row heights) and padding
between dives later on.

The layout class still support NxM dives per page, so this can be made
optional as well so that users can print, say 10x7 dives on an A2 page.

[PATCH 1/4] Helpers: add get_cylinder_used_gas_string()
[PATCH 2/4] Profile: use a 10px font when printing profile text
[PATCH 3/4] Print: provide means to print profile tables
[PATCH 4/4] Print: small adjustments to table printing

lubomir
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