[Calibration] LuIndex

Description

Part of #12.

• adjusted default and large size to feed Wikipedia archive to Lucene
• add --linedoc and --dirwalk option to specify doc-per-line format and directory walk;
• add uncompressed Wikipedia archive used for Lucene benchmark;
• modified benchmark harness;
• download and prepare Wikipedia data at build time (if checksum failed)
• currently referencing the Wikipedia data relative to scratch, this needs to be changed later with external data feature.

Performance Numbers

machines	default (sec)	large (sec)
Intel i7-6700k w. 16GB RAM (fisher.moma)	10.115	469.390
AMD FX-8320 w. 8GB RAM (lynx.moma)	17.808	845.633

Checklist before merge

• what to do with the big data (8.5G); leave it as it is, or use Git LFS, or merge #11 in.
• squash into 1 comment.