Provide a UI notice on completion of the build-ca command
Support v2-style clean-all command alias in help display

This change also removes the note about historical command naming.
Add support for show-req & show-cert commands

These commands allow detailed req/cert info to be shown in a
human-readable format.
Update README.quickstart to match current command syntax

Some minor text changes to make it more readable are included.
Update vars.example with Windows path requirements for mksh

The Win32 release will rely on mksh, which cannot use single-backslashes
in paths. We provide info and samples for the users in vars.example.
Improve notes about key sizing options
Update org DN default values

Use spaces in the samples and make the org name more generic.
Re-structure env-vars under EASYRSA_* namespace

This is a compatability-breaking change, but will prevent possible
env-var overlap with other programs. This is especially important now
that the 3.x codebase allows env-var values to override both 'vars' and
CLI options.

In particular, the BATCH to EASYRSA_BATCH change prevents accidental
removal of files when running init-pki, but it was a good time to change
the namespace for the other globals/exports as well.
Shell compatability changes, including use of printf & awk

printf is used in place of echo commands for POSIX compability.

All usage of grep & sed has been replaced with awk for convenience, and
less reliance on external (not provided by shell) commands.

Only the openssl command is referred to by variable now. Broken shells
that don't provide POSIX-required utilities can use aliases if needed.
Improve program flow in sign_req() creating the extensions file

Moved back to using cat as it is POSIX required. The entire write-out is
now part of the test for failure as well, not just the critical crt_type
file.
Variable cleanup: mostly EASYRSA_PKI aggregation

This change pulls the EASYRSA_PKI path out of many lines by placing them
in func-local variables that are re-used.