Consolidate in-repo documentation (#3143)

* move doc/misc to top level, add READMEs

* Move docs -> doc/devel

This also consolidates the _three_ documents describing (differently)
how to build Taskwarrior into a signle document.

doc/devel/contrib/development.md

@@ -0,0 +1,48 @@
+# Developing Taskwarrior
+
+## Satisfy the Requirements:
+
+ * CMake 3.0 or later
+ * gcc 7.0 or later, clang 6.0 or later, or a compiler with full C++17 support
+ * libuuid (if not on macOS)
+ * python 3 (optional, for running the test suite)
+ * Rust 1.64.0 or higher (hint: use https://rustup.rs/ instead of using your system's package manager)
+
+## Obtain and Build Code:
+```
+    $ git clone --recursive https://github.com/GothenburgBitFactory/taskwarrior taskwarrior.git
+    $ cd taskwarrior.git
+    $ git checkout develop               # Latest dev branch
+    $ git submodule init                 # This is now done by cmake as a test
+    $ git submodule update               # Update the libhsared.git submodule
+    $ cmake -DCMAKE_BUILD_TYPE=debug .   # debug or release. Default: neither
+    $ make VERBOSE=1 -j4                 # Shows details, builds using 4 jobs
+                                         # Alternately 'export MAKEFLAGS=-j 4'
+```
+
+This will build several executables, but the one you want is probably `src/task`.
+When you make changes, just run the last line again.
+
+## Run the Test Suite:
+
+First switch to the test directory:
+
+```
+    $ cd test
+```
+Then you can run all tests, showing details, with
+```
+    $ make VERBOSE=1
+```
+Alternately, run the tests with the details hidden in `all.log`:
+```
+    $ ./run_all
+```
+Either way, you can get a summary of any test failures with:
+```
+    $ ./problems
+```
+
+Note that any development should be performed using a git clone, and the current development branch.
+The source tarballs do not reflect HEAD, and do not contain the test suite.
+Follow the [GitHub flow](https://docs.github.com/en/get-started/quickstart/github-flow) for creating a pull request.