Allow FB-known macros in replication.conf

[pavel-zotov]

For QA tasks, it will be useful to have ability to specify macros, say "$(dir_sample)", instead of absolute paths in the replication.conf:

database="$(dir_sample)/qa/dbrepl.fdb"
{
	journal_source_directory="$(dir_sample)/qa/dbmain.fdb.LogArch"
	. . .
}
database="$(dir_sample)/qa/dbmain.fdb"
{
	journal_archive_directory="$(dir_sample)/qa/dbmain.fdb.LogArch"
	. . .
	journal_directory="$(dir_sample)/qa/dbmain.fdb.ReplLog"
}

Currently one need to write absolute path, so replication.conf can not be moved into another place w/o further modifications.