Support subprojects

[mrexodia]

Currently a [project] causes automatic regeneration to stop (for consistency reasons, you don't want to regenerate another cmkr project's files). Can be solved like this:

[project]
name = "root"

[subdir.project1]

[project]
name = "project1"
subproject = true
parent = "root"

Either the subproject or the parent project could make it so root would work. The downside of using subproject is that accidentally setting it in a root project would falsely cause regeneration across different repositories.

[mrexodia]

A related issue is where you include a subdirectory of another project (without including the subproject itself):

Root cmake.toml:

[project]
name = "root"

[subdir."subproject/lib"]

In this case subproject/cmake.toml is never encountered, so subproject/lib/CMakeLists.txt will be regenerated, which is a bug.

Actually it looks like this case is handled properly, but some testing is needed...