src: deprecate "flow table" syntax, replace it by "meter"

src: deprecate "flow table" syntax, replace it by "meter"

According to bugzilla 1137: "flow tables" should not be syntactically
unique.

"Flow tables are always named, but they don't conform to the way sets,
maps, and dictionaries work in terms of "add" and "delete" and all that.

They are also "flow tables" instead of one word like "flows" or
"throttle" or something.

It seems weird to just have these break the syntactic expectations."

Personally, I never liked the reference to "table" since we have very
specific semantics in terms of what a "table" is netfilter for long
time.

This patch promotes "meter" as the new keyword. The former syntax is
still accepted for a while, just to reduce chances of breaking things.
At some point the former syntax will just be removed.

Closes: https://bugzilla.netfilter.org/show_bug.cgi?id=1137
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Acked-by: Arturo Borrero Gonzalez <arturo@netfilter.org>