Generate the object layer from the catalog's object model

[estebanzimanyi]

GoMEOS ships a generated flat FFI layer and a hand-written idiomatic one, so
every class, method and conversion above the wrappers is written and maintained
by hand. The catalog already states that layer: objectModel.lattice carries the
temporal tree, companions the Box, Collection and Value hierarchies, and
classes.<Class>.methods assigns each public MEOS function to the class it is a
method of, under its canonical camelCase ooName. MEOS.NET projects the same
model through its own tools/objectgen.py; this is the Go projection of it.

Go spells inheritance as embedding, so TBool embeds TAlpha embeds Temporal
and a parent's methods are promoted. Each instance carries the MEOS pointer, and
the two packages exchange it as an unsafe.Pointer, because cgo types are
package-scoped and *C.Temporal in functions is not the same Go type as one
declared here.

THE SIGNATURES COME FROM codegen.SIGNATURES, so the two generators cannot
disagree. MEOS declares bool tbool_value_at_timestamptz(..., bool *value) --
four parameters, one of them written through -- while the wrapper takes three and
answers two values. Reading the C signature would reconstruct a shape the wrapper
does not have. The table is filled by RUNNING the flat generator, so which
functions have a wrapper is decided in one place and this file holds no second
copy of what that generator skips.

ABSENCE STAYS AN OPTIONAL, in the shape this repository already merged: where
MEOS answers a flag and writes the value out, the method answers
(value, ok, error) with ok false leaving the value at its zero and the error
nil. TBool.ValueAtTimestamptz is generated to exactly what #21 hand-wrote.

MEASURED against a catalog derived at current master: 115 classes, 1256 methods,
105 deferred, each deferral naming the parameter or result that stopped it rather
than being dropped silently. go build ./types ./functions and go vet ./types
both exit 0, gofmt -l reports 0 of 116 files, and a second run of the generator
reproduces the tree byte for byte.

The layer is ADDITIVE: the root package is untouched, so no published name moves.

Stacked on #25 (the snapshot refresh), which the generated layer calls into: types/geometry.go uses functions.GeomArea and functions.GeomAzimuth, which the pre-refresh snapshot does not declare.