Extended wildcard support for virtual host names

[lmakarov]

We currently support projects matching the following virtual host rules:

• exact match: example.com (code)
• wildcard match with multiple values: example.com,*.example.com,example2.com (code)

This is a proposal to support *.VIRTUAL_HOST.* wildcards (single and/or multi-value options).

nginx does not support this kind of wildcard, but does support regexp virtual hosts:
http://nginx.org/en/docs/http/server_names.html
For nginx, the virtual host would need to be defined as: ^(.+\.)?VIRTUAL_HOST_ESCAPED(\..+)?$

In proxyctl we will also have to make changes to the logic handling project lookup in the start() function.

Once implemented, this will simplify the sandboxing use case, as it will no longer be necessary to adjust project's VIRTUAL_HOST settings to add the base domain for the sandbox environments.