Move `build` and `vcs` into `tasks`
Remove unnecessary logging import
Move VERBOSE to its own module

This removes `xnt` -> `xnt.tasks.build.tex` -> `xnt` circular dependency.
Convert `expandpath` to noop variation
Refactor: make `__init__.py` more 'import only'

Move the task definitions from `xnt.tasks.__init__py` to
`xnt.tasks.core_tasks.py` and use `xnt.tasks.__init__.py` as an import
module. Everything _within_ the `xnt.tasks` module should not depend on
`xnt.tasks` directly; dependencies should be satisfied directly: e.g.,
depending on `xnt.tasks.core_tasks` for methods like `__call__` and
`__apply__`.

`xnt.tasks` now does the job `xnt` was doing: expose all task functions. As
such, `xnt` now just exports the names from `xnt.tasks` as part of its
definition. Modules outside `xnt.tasks` can safely depend on `xnt.tasks`
exclusively.
pylint: W0703, catch RuntimeError instead
Locally disable pylint R0912
Remove deprecated pytlint configuration options