Any text written after the coordinate input will automatically be
forwarded to the output stream. Text in columns before the coordinate
input is discarded in the output. This works for any combination of -c, -t
and -z parameters:

$ echo 12 56 100 2018.0 comment comment | cct +proj=merc
 1335833.8895   7522963.2411      100.0000     2018.0000 comment commen

$ echo text 12 56 100 2018.0 comment | cct -c 2,3,4,5 +proj=merc
 1335833.8895   7522963.2411      100.0000     2018.0000 comment

$ echo text 12 56 comment | cct -c 2,3 -t0 -z0 +proj=merc
 1335833.8895   7522963.2411        0.0000        0.0000 comment

$ echo 12 56 comment | cct -t0 -z0 +proj=merc
 1335833.8895   7522963.2411        0.0000        0.0000 comment

Closes #918

Added the version of introduction and removed comment about angular and
linear output (it's an internal implementation detail that users doesn't
need to be aware of).

Specify number of decimals to display when transforming coordinates with either proj, cs2cs or cct.

proj only does projections, hence we should use the word conversion instead of transformation in this context.

Closes #981