Massage e2.conf searching/parsing into a single function.

Massage e2.conf searching/parsing into a single function.

Move read_global_config() into e2lib.get_global_config().

Collapse reading of .e2/e2config into get_global_config(). Remove need for
e2lib.globals.cmdline vector which was only used to pass --e2-config
around. Remove e2lib.sete2config() which used to set the E2_CONFIG
environment variable for calling another e2 tool.

In e2-fetch-project, pass arg vector to e2-install-e2. Previously this
relied on E2_CONFIG being set. Now all arguments, --e2-config, warning
flags and verbosity options are passed along.

The returned config table is locked to detect errors.

Update ldoc comments while cleaning up.

Signed-off-by: Tobias Ulmer <tu@emlix.com>