[FEATURE] Accept kwargs for execute and executeStmt

[jeffreyaven]

Feature Description
Allow kwargs to be supplied to the execute and executeStmt methods, named arguments supplied to these methods will override either equivalents which were supplied in the StackQL class constructor.

Example(s)

from pystackql import StackQL
provider_auth =  {
    "github": {
        "credentialsenvvar": "GITHUBCREDS",
        "type": "basic"
    }
}
stackql = StackQL(auth=provider_auth, output="csv")
print(stackql.execute("select id, name from github.repos.repos where org = 'stackql'"))

# returns: 
# id,name
# 443987542,stackql
# 441087132,stackql-provider-registry
# 455730530,pystackql
#456722161,stackql-jupyter-demo
# ...

print(stackql.execute("select id, name from github.repos.repos where org = 'stackql'", output="json"))

# returns:
# [{"id":"443987542","name":"stackql"},{"id":"441087132","name":"stackql-provider-registry"},...]