Bookmark name as hostname for cli args

Description

Bookmark name as hostname for CLI arguments
- It is now possible to provide the name of the bookmark you want to connect to, instead of the address in command line arguments
To do so it is enough to run termscp as follows:
```
termscp -b <bookmark-name>
```
If the password is stored in the bookmark, it will be used, otherwise you will be prompted to type the password in.

Please select relevant options.

[ ] Bug fix (non-breaking change which fixes an issue)
[x] New feature (non-breaking change which adds functionality)
[ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)
[x] This change requires a documentation update

[x] My code follows the contribution guidelines of this project
[x] I have performed a self-review of my own code
[x] I have commented my code, particularly in hard-to-understand areas
[x] My changes generate no new warnings
[x] I formatted the code with cargo fmt
[x] I checked my code using cargo clippy and reports no warnings
[x] I have added tests that prove my fix is effective or that my feature works
[x] I have introduced no new C-bindings
[x] The changes I've made are Windows, MacOS, UNIX, Linux compatible (or I've handled them using cfg target_os)
[x] I increased or maintained the code coverage for the project, compared to the previous commit

[x] regression test: address argument still work correctly
[x] regression test: bookmark client still works correctly in auth activity
[x] if -b option is provided and the bookmark exists with the password, I connect directly to the associated host
[x] if -b option is provided and the bookmark exists with no password, I get prompted for the password and then I can connect to the associated host
[x] if -b option is provided and the bookmark DOES NOT EXIST, an error is shown