Inclusion of planning info (*DEADLINE*, *SCHEDULED*, and *CLOSED*) can
be controlled via the `p` export option: setting the option to `t` will
add all planning information in a *Plain* block below the respective
headline.
This gives a pure way to insert an ersatz file into a FileTree.
In addition, we normalize paths both on insertion and on
lookup, so that "foo" and "./foo" will be judged equivalent.
The level of headers in included files can be shifted to a higher level
by specifying a minimum header level via the `:minlevel` parameter. E.g.
`#+include: "tour.org" :minlevel 1` will shift the headers in tour.org
such that the topmost headers become level 1 headers.
Fixes: #4154
The org reader test file had grown large, to the point that editor
performance was negatively affected in some cases. The tests are spread
over multiple submodules, and re-combined into a tasty TestTree in the
main org reader test file.
