DOC: Add an anchor for the Exec section

Signed-off-by: Toni Gundogdu <legatvs@gmail.com>
DOC: quvi-get(1): Revise the output-regex description

Other:
* Use the exec anchor throughout the document

Signed-off-by: Toni Gundogdu <legatvs@gmail.com>
DOC: --exec: Add the missing %e sequence

Signed-off-by: Toni Gundogdu <legatvs@gmail.com>
DOC: Use linkman with quvirc where applicable and unused

Signed-off-by: Toni Gundogdu <legatvs@gmail.com>