1. Disable the MySQL client and LZO library by default when building the Doris.
MySQL client library is used for MySQL external table feature.
This feature will be replaced by the new ODBC external table soon.
LZO library is used to compress/decompress data of some old data format of Doris,
which is no longer used anymore.
2. Add missing license to some files.
3. For all non-Apache-License code, all are explained in NOTICE file and the corresponding license is declared.
4. Remove the js source code from webroot, it will be downloaded as thirdparty
This CL mainly made the following modifications:
1. Reorganized SegmentV2 upgrade document.
2. When the variable `use_v2_rollup` is set to true, the base rollup in v2 format is forcibly queried for verifying the data.
3. Fix a problem that there is no persistent storage format information in the schema change operation that performs v2 conversion.
4. Allow users to directly create v2 format tables.
