Improve search symbol table

[subins2000]

• Adds varnam_new_search_symbol :

Symbol table search had a fatal flaw :

var searchCriteria Symbol
searchCriteria.Pattern = "a"
searchCriteria.AcceptCondition = 0

Varnam omitted a search criteria by seeing if the value is a default struct value of Go. Go's default struct value is 0 which means one can't apply a search criteria of value 0. The solution applied in this PR to this is to set default value -1 by calling func NewSymbol(): Symbol. So now:

searchCriteria := NewSymbol()
searchCriteria.Pattern = "a"
searchCriteria.AcceptCondition = 0

• Added all varnam configuration vars to varnam_config(). Previously used functions like varnam_set_dictionary_suggestions_limit has been DEPRECATED.

[subins2000]

Ignoring test failure cause it depends on https://github.com/varnamproject/schemes/pull/4 which depends on this PR :D