Update documentation for the FT.* commands

[BagritsevichStepan]

We need to update documentation for the SEARCH commands.

Currently supported commands:

static void FtCreate(CmdArgList args, const CommandContext& cmd_cntx);
static void FtAlter(CmdArgList args, const CommandContext& cmd_cntx);
static void FtDropIndex(CmdArgList args, const CommandContext& cmd_cntx);
static void FtInfo(CmdArgList args, const CommandContext& cmd_cntx);
static void FtList(CmdArgList args, const CommandContext& cmd_cntx);
static void FtSearch(CmdArgList args, const CommandContext& cmd_cntx);
static void FtProfile(CmdArgList args, const CommandContext& cmd_cntx);
static void FtAggregate(CmdArgList args, const CommandContext& cmd_cntx);
static void FtTagVals(CmdArgList args, const CommandContext& cmd_cntx);

In documentation we have only:

FT._LIST
FT.CREATE
FT.DROPINDEX
FT.INFO
FT.PROFILE
FT.SEARCH

[vyavdoshenko]

The list of supported commands should be updated as well.

[romange]

@BagritsevichStepan you can split this issue with more clarity if needed.