Remove _mode_to_query, consolidate with QueryRunner (#118)

.gitignore

gpt_index/indices/base.py

gpt_index/indices/data_structs.py

gpt_index/indices/keyword_table/base.py

gpt_index/indices/list/base.py

gpt_index/indices/query/list/embedding_query.py

gpt_index/indices/query/query_map.py

gpt_index/indices/query/query_runner.py

gpt_index/indices/query/schema.py

gpt_index/indices/query/tree/embedding_query.py

gpt_index/indices/tree/base.py

gpt_index/indices/vector_store/faiss.py