lib/opts: add flag `options_before_rest`

Signed-off-by: Jean Privat <jean@pryen.org>
nit: use OptionContext flag options_before_rest

Signed-off-by: Jean Privat <jean@pryen.org>
modelize: 4 -v are needed fo method-level informations

Signed-off-by: Jean Privat <jean@pryen.org>
tests: with niti put the options before the program

Signed-off-by: Jean Privat <jean@pryen.org>
toolcontext: hide some really internal options so they do not appears on --help

* --bash-completion
* --stub-man
* --set-dummy-tool
* --no-main

These options are still recognized, bash-completed and in the manpage

Signed-off-by: Jean Privat <jean@pryen.org>
tests: update sav/test_toolcontext*

Signed-off-by: Jean Privat <jean@pryen.org>
contrib/online_ide: update signature of `compute_nit_dir`

Signed-off-by: Jean Privat <jean@pryen.org>