[API][Docs] Rename APIs that create schedules; allow users to return tensors

[seanlatias]

• Rename all make_* to create_*
• Users only need to specify the inputs once when first create a scheme or a schedule. Users do not need to specify the inputs again when lowering or building the function. The returned tensors do not need to be specified in the inputs list.
• Users can now return tensors within an algorithm. The returned tensors will be treated as inputs to the final built function.
• Users can now specify the default data type via the init API.

We show an example here.

# speficy the default data type for all tensors
hcl.init(hcl.Float())

A = hcl.placeholder(...)

def foo(A):
  B = hcl.compute(A.shape, lambda x: A[x] + 1)
  C = hcl.compute(A.shape, lambda x: A[x] + 2)
  return B, C

# only need to specify the inputs here
# note that the inputs list does not include B and C
# it is also not possible for users to include B and C, which are inside a function
scheme = hcl.create_scheme([A], foo)
# apply quantization schemes
schedule = hcl.create_schedule_from_scheme(scheme)
# apply compute cutomization primitives

print hcl.lower(schedule) # no need to specify inputs list here
f = hcl.build(schedule) # same as above

_A = hcl.asarray(...)
_B = hcl.asarray(...)
_C = hcl.asarray(...)
f(_A, _B, _C) # the generated function has 3 arguments

• Edit the introduction page
• Update the online documentation with only pages that are useful to the users