Simplify conference budgeting by clarifying profit reporting

Currently, we ask conferences to return $11/head plus a negotiated
"surplus component".

However, our financial reports only report a single "profit" from the
conference; it's not clear from our reports how much of this covers LA
expenses and how much is genuine profit.

This change simplifies accounting and reporting by removing the
surplus component.

It is invisaged this would be complemented by:
 - A change from $11/head to 6% of total revenue as the fee LA charges
 - A change in reporting to show this as a fee returned to LA,
 reducing the reported "profit" by this amount

The "Budgeting" section already suggests that conference budgets
should "consider both direct concerns of the conference, and long-term
investments in the community". This change would make it clearer how
much profit is available for these long-term concerns.

It is anticipated that most events will want to prioritise these items
as "If we have space in the budget" items.

subcommittee_policy_v2.md

@@ -106,7 +106,9 @@ Handover and Delegation of Authority
 
 ### Conference Proceeds
 * The council takes care of a number of expenses conferences incur, such as insurance, accounting/tax issues, credit card processing fees. The council will provide the amounts/formulas for these entries to be included as expenses in the subcommittee budget.
-* Conferences must nominate a level of contingency for unforeseen expenses, and may be asked to nominate a surplus component in their budget. These amounts must meet the approval of council.  The surplus proceeds of a conference contribute to the ongoing financial stability of Linux Australia and its ability to facilitate and support open technology communities.
+* Conferences must nominate a level of contingency for unforeseen expenses which must meet the approval of council.
+* A Conference may earmark any excess proceeds to be spent on future events, for supporting the community related to the conference, or to support international communities related to the conference.
+* Conference are encouraged to direct a portion of their surplus proceeds to contribute to the ongoing financial stability of Linux Australia and its ability to facilitate and support open technology communities.
 
 ### Reporting
 * The subcommittee must report to the Linux Australia council regularly, in the form of minuted decisions and reports made by the subcommittee, including any budget updates.