Support for non-solid external compression

arc1.arc updated:

• added translation support for 40+ strings. dear translators, please update your files
• arc.ini: adding "solid=0" to external compressor definition forces FreeArc to create separate solid block for every file compressed by this method (or by chain starting with this compression method):

[External compressor:jpg]
mem = 10
packcmd = timer packjpg $$arcdatafile$$.jpg
unpackcmd = timer packjpg $$arcdatafile$$.pjg
datafile = $$arcdatafile$$.jpg
packedfile = $$arcdatafile$$.pjg
solid = 0