Fine-tune copyright printing.

Based on discussion in earlier changes, made the copyright on by
default.  It is now possible to suppress it while keeping other parts of
the startup header with -nocopyright.

Simplify the copyright printing code and make the output more in line
with the rest of the startup header (left-aligned etc.).  Move the
copyright to the beginning of the header to have all diagnostic
information available under it; that makes it easier for the user (and
for us in bug reports) to spot all the relevant information.

Also adjust the wording of the license text; LGPL does not automatically
place a user program that calls GROMACS under the same license, so
changed "This program" to "GROMACS".  Made a similar clarification to
the "Written by" text.

Part of #1209.

Change-Id: If104074995db891702dd9eb410fe811408add4ad