refacored index add operations

refactored code to use indexStore

Fdb:  filebase import and export

See merge request !166

Fdb cache eviction

See merge request !164

Fix: Build failed due to unused vars

See merge request !163

1. Fix: Build is breaking due to unused vars

Chore: Remove unwanted logs

See merge request !162

1.  Chore: Remove unwanted logs

fdb import with updating index entries

See merge request !161

1) import with updating index entries instead of replacing existing index file
2) atomic replace support for darwin platform

fix: clear file pointer cache after data import in fdb

See merge request !160

added feature to import/export as fdb data in zip format

See merge request !158

added feature to import/export as fdb data in zip format

fix: exporting index files by filtering with queries

See merge request !156

Add: Lazywriter support for Normal and append bucket

Closes #6

See merge request !157

1. Fix: got length of cyphertext is less than 0 error on empty file read.

1. Fix: Disable encryption for append bucket as no way to read encrypted data.

fix: exporting index files by filtering with queries 

1. Add: Lazy writer for append bucket

1. Fix: Lazy writer fails to write data to disk due to invalid json. The "data" passed to GenSecKey function is string.

pkcs7 : padding data functions added in securitymdl

See merge request !154

1. Add: Enable lazy writing for normal bucket

added feature to export and import data into fdb

See merge request !152

added feature to export and import data into fdb

Fix: Index file not created in some cases.

See merge request !151

Fix: Index file not created in some cases. Ex. For asset FDB on another drive.

removed unnecessary logs

See merge request !149

removed unnecessary logs

Fix: Decryption and Normal bucket errors

See merge request !147

1. Fix: Failed to get json data from pack on asset update.
2. Fix: Failed to get content-type from meta data.