Bring Tazel Custom Commands and Tazel Options from the legacy Tazelfeature/custom-commands-and-options

The code and tests come from Progmasoft/tazel-legacy, with the packages
renamed so that the shared lexer sits beside both users:

- com.progmasoft.tazel.custom.commands        -> com.progmasoft.tazel.dsl.custom
- com.progmasoft.tazel.custom.commands.lexer  -> com.progmasoft.tazel.dsl.custom.lexer
- com.progmasoft.tazel.custom.commands.parser -> com.progmasoft.tazel.dsl.custom.parser
- com.progmasoft.tazel.options                -> com.progmasoft.tazel.dsl.options

tazel custom runs a command of the nearest tazel_custom.txt in the
directory of that file, or lists the commands; the name matching, <N>
and <*> arguments, the -- separator, s(...) shell steps (CMD on Windows,
sh elsewhere) and the strict-process check are those of the legacy
Tazel. tazel_options.txt is read as before: a sandbox asked for in any
file at or above the directory stops the command, since Tazel has no
MicroVM to start yet.

The process interface (driver.Processes) and the suggestions under
errors come along; program lookup on PATH is driver.Programs, the part
of the legacy Toolchain that is not about Tala tools. OperatingSystem
becomes the Os of the project files. An unknown command now gets a
"did you mean" hint.

The 33 legacy tests of these parts pass against a smaller fixture.

0 files changed, 0 insertions, 0 deletions