Enable 'bash-rollup-always-inline' flag

[zanerock]

Overview

By default, bash-rollup will only include a file once. Sometimes, you really do want to 'inline' code.

Deliverables

• Enable a bash-rollup-always-inline' flag which can be included after sourceandimport` statements. If present, then skip the "is this file included" check and always include the file contents in place.
• Once included via an always inline, then anything included by tracing through the always inlined script is always inlined. I.e., the 'always inline' flag is sticky for all sub-includes.
• Emit a warning with line number and line text if a recursively 'always inlined' include is not explicitly marked. E.g.:

  WARNING: 'source foo.sh' @ line 25 in './inlinable.sh' is being processed with 'always inline' implied, but it is not explicitly set.