checks functions

[Thelvaen]

Hello,

On my fork, there's a couple of check that could be reused on the main project :

• test for duplicates char in sequence in the password, ie totoAAAverySecurePassword will fail because of the AAA,
• test if the first char is alphanumeric or not, some apps might fail due to 1st char being alphanumeric,
• test for numerical sequence in the password (123, 234, ...)

[Thelvaen]

I saw a bit too late that the "no_special_at_ends" check was already doing the 1st char non alpha check :)

[coudot]

You can propose pull requests for this (one for each feature)