Add support for named parameters

[chshersh]

MySQL doesn't support named parameters on the protocol level. So the only possible way to implement named parameters in our library is the following:

1. Introduce data type data NamedParam = NamedParam Text Param (where Text is the name of the parameter).
2. Implement functions executeNamed and queryNamed with types:

queryNamed :: FromRow row => MySQLConn -> Query -> [NamedParam] -> IO [row]

These function will parse Query and replace all occurrences of :nameOfTheParameter with ? and rearrange arguments in [NamedParam] list according to their occurrence in the Query. And then these functions just delegate their arguments to query and execute functions.

Regarding parsing of Query: I propose that after : only alphanumeric characters and underscores are allowed. I hope that : is not used anywhere in MySQL...

Any thoughts on this?

[chshersh]

This issue is done 🎉 🎆