Resolving Issue #2 (ValueError: top-level default class 'main' cannot be renamed when using <include> with <default> block)

[srinjoy-not-007]

There is an error in the placement of the top default tag. The default tag with the acker_solver_param class should be contained within the top default tag. The correction that I propose:

`

<default class="acker_solver_param">
	<!--solver impedance and reference(?) for ackerman equality constraint-->
	<!--default solimp: "0.900 0.950 0.001"-->
	<!--default solref: "0.020 1.000"-->
	<!--solref: (timeconst, dampratio)
		b = 2 / (dmax * timeconst)
		k = d(r) / (dmax * dmax * timeconst * timeconst * dampratio * dampratio)
	-->
	<equality solimp="0.9950 0.9990 0.0001" solref="0.0100 0.7500"/>
</default>

`