Replaces Artemix/Yafits video by a Yafits 2d or 3d video according to the displayed page.

See merge request artemix/yafits!4

The value was calculated. The exact value is displayed when the user clicks on the image.

Adds a video icon.

Modified the content of the prepended to illustrate more clearly the COUNT function and the clauses LIMIT and OFFSET

Conflicts:
	docker-compose.yml

Removed doublons in the knowFields dropdown menu, added examples with LIMIT and OFFSET, filter queries results with more than MAXROWS rows.

Calculation of SQLITE_MAXROWS from env var with default value (1000) and transmit the value to the client side.

Added the env var YAFITS_SQLITE_DIR for yafitssel

See merge request artemix/yafits!2