Search authors based on known names

Sometimes the authorship notices are hardly detectable such as here https://github.com/torvalds/linux/blob/master/drivers/net/ifb.c :
```
The original concept is based on what is known as the IMQ
driver initially written by Martin Devera, later rewritten
by Patrick McHardy and then maintained by Andre Correa.
```
or there https://github.com/torvalds/linux/blob/master/net/ipv6/reassembly.c
```
* Fixes:
* Andi Kleen Make it work with multiple hosts.
* More RFC compliance.
*
* Horst von Brand Add missing #include
* Alexey Kuznetsov SMP races, threading, cleanup.
*
```
We could in some cases improve the grammar for author detection. Alternatively we could assist this detection with a list of known author names/emails.

This new feature could take a few different forms:
- 1. a generic "search" feature for keywords as in https://github.com/nexB/scancode-toolkit/issues/1751
- 2. a specific enhanced author detection

For 1. We would have a new option like a `--search-from ` and this would used to return a new file-level attribute that would be similar in structure to the author or copyright output. The implementation could be a simple "naive" regex-based search, or based on an automaton created on the fly (similar to the automaton used in license detection)

For 2. we would extend the author detection and grammar to extend it with a like of patterns like in 1.